1. Field of the Invention
The present invention relates to a voice modulating apparatus, and particularly, to an apparatus and a method for voice modulation in a mobile communication terminal.
2. Description of the Background Art
Voice and sound is a kind of energy, that is, vibration generated from a source of sound delivered as making air as a medium. Physically, the sound has three elements such as the times of vibration, that is, frequency, amplitude, and duration. The voice of human being is a compound of sounds having various frequencies. Therefore, a pitch of the voice is not only decided by a size of the frequency, but a difference in tone by which various vowels and consonants are distinguished is generated by constitution of frequencies.
The human beings generate voice frequency of 100˜400 Hz generally, and a frequency range that the human beings can hear is 15˜20,000 Hz. The voices of human beings have their own properties, that is, different pitches and lengths of sound. Human brain remembers the differences, and therefore, the human beings can recognize the speaker only with his/her voice.
Voice modulation is to change the properties of voice intentionally.
FIG. 1 is a block diagram showing a general mobile terminal related to a voice processing.
As shown therein, the mobile terminal comprises: a voice input unit 10 being inputted the voice of subscriber and generating an analog voice signal; an audio processor 30 for converting the analog voice signal into a digital signal; and a mobile station modem (hereinafter, referred to as ‘MSM’) 40 processing the digital signal to be suitable for wireless transmission.
General operation of the mobile terminal will be described as follows.
The voice input unit 10 is a device for collecting and converting the voice of the subscriber, and the voice input unit 10 converts the collected subscriber's voice into an analog signal and transmits it to the audio processor 30. The audio processor 30 amplifies the converted analog signal, and converts the signal into a digital signal of pulse code modulation (PCM) data form. And the converted digital signal is transmitted to the MSM 40.
The MSM 40 convolutionally encodes the received digital signal so as to detect and correct an error in transmission, scrambles the signal in order to ensure the privacy, and generates an IQ signal by 4-phase modulating using a pair of pilot PN code. Then the IQ signal is converted into a radio frequency (RF) signal as passing through a predetermined procedure, and discharged wirelessly through an antenna.
The MSM 40 is a circuit performing same functions as those of a central processing unit (CPU) in a computer, comprises an encoder, an interleaver, a deinterleaver, a viterbi decoder, a mod/demodulator, and a vocoder, etc., and controls most functions processed in the mobile terminal.
As described above, the conventional voice processing unit puts an emphasis on preventing the modulation and deformation of voice, and restoring the voice similarly to the original sound in the process of converting the voice into the signal and the code. The conventional mobile terminal is faithful to its own objects, however, can not satisfy the various desires of the subscriber since it does not have the functions of voice modulation and intentional voice modulation by which the subscriber is able to be protected from telephone harassment.